Raps knuckles refer to the action of lightly drumming one's knuckles on a surface to produce a sharp sound. The antonyms for this phrase are a bit tricky as there isn't an exact opposite of this action. However, some words that can be used to contrast this phrase include gently rubbing the knuckles, patting the knuckles, or caressing the skin instead of hitting it. Alternatively, the exact opposite, in terms of sound, would be to silence or muffle the knuckles. Nevertheless, raps knuckles is usually associated with disciplinary action, and antonyms for this might include praise, applaud, or cheer, which suggest an expression of appreciation, rather than reprimand.